1. Field of the Invention
The present invention relates to a liquid toner used for an image forming apparatus. More particularly, the present invention relates to a test apparatus to evaluate electrical properties of a liquid toner and a test method for the same in which electrical properties of the liquid toner may be evaluated without printing with the liquid toner using an image forming apparatus.
2. Description of the Related Art
Generally, a wet image forming apparatus based on a liquid toner has several advantages in that it can realize high resolution image because toner particles are small. Additionally, high-speed printing is possible, and the printing cost per page is inexpensive because a small amount of toner is required.
The liquid toner used for a wet laser printer is made by dispersing toner particles made of additives, such as a high polymer resin, a pigment, a charge control agent, and a dispersing adjuvant, in a solvent, i.e., a hydrocarbon based liquid carrier. In this case, the liquid toner contains solid components, such as the high polymer resin, the pigment, the charge control agent, and the dispersing adjuvant, within the range of 10% by weight and the solvent components within the range of 90% by weight.
FIG. 1 illustrates a scheme of a wet image forming apparatus that performs printing using the aforementioned liquid toner. Referring to FIG. 1, the liquid toner is transferred on a paper P by a transfer roller 40 through a transfer belt 30 after a developing device 10 develops an electrostatic latent image of a photo-resist body 20. The paper P, on which toner particles are transferred, contains solvent components and solid components. The solvent components are volatilized and the solid components are hardened while passing through a fixing portion 50 of high temperature, thus forming images on the paper P. In FIG. 1, the wet image forming apparatus includes four developing devices 10 to realize color images. A reference numeral 31 denotes a cleaning means that cleans a toner remaining in the transfer belt 30. The wet image forming apparatus may be provided in such a manner that the liquid toner is directly transferred on the paper P from the photo-resist body 20 without utilizing the transfer belt 30.
In the aforementioned wet image forming apparatus, the quality of final images on the paper, i.e., the printing quality, depends on the electrical properties of the liquid toner. Therefore, the quality of the images to be printed on the paper may be predicted by evaluating the electrical properties of the liquid toner. Until now, the charge amount per unit weight of toner particles, i.e., q/m(μC/g), has been tested to evaluate the electrical properties of the liquid toner. In this case, q/m can explain the electrical properties of the liquid toner at the transfer operation T0 (see FIG. 1) from the developing device 10 to the photo-resist body 20, but cannot explain those at the transfer operation T1 from the photo-resist body 20 to the transfer belt 30 and the transfer operation T2 from the transfer belt 30 to the paper P through the transfer roller 40. Therefore, the printing had to be performed by an image forming apparatus with a special liquid toner, so that the electrical properties of the liquid toner that affect the printing quality can be evaluated by referring to the printing result.
As described above, the image forming apparatus is required to evaluate the printing quality if printing is performed with a special liquid toner. In this case, problems occur in that the inconvenient operation is required, and significant time and cost are required to evaluate the printing quality.